[Chameleon] How to use ExpressionBuilder?

[Pssdal Bakosurtanal]

Dear expert,

When I tried to access http://myserver/chameleon/samples/sample_roi.phtml on
the chameleon sample. (using chameleon 2.2)
Everythings is ok until I tried to click on "Build Filter" on the tab tools,
the popup error appeared with the message "There is no active layer
selected. You must a layer inorder to use this tool". How to to activated
the layer? Does anyone success access this sample above?

If i would like to use expression builder, should I am working with WMS or
WFS?

Thank you for your help.
Best Regards,
PSSDAL
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